1. Field of the Invention
The present invention relates to a MOS type solid-state image pickup element, a method of manufacturing the same, and an electronic apparatus using the same.
2. Description of the Related Art
A CMOS type solid-state image pickup element having a surface radiation type structure is shown as an example of a current solid-state image pickup element in FIG. 7. In a surface radiation type solid-state image pickup element 201, signal processing portions 229 and a wiring layer 223 are formed in an upper layer relative to a photoelectric conversion portion (composed of photodiodes: PDs) 222. The wiring layer 223 is structured by laminating wirings 224 and insulating layers 225. In addition, a color filter 227 and an on-chip lens 228 are formed in this order on the wiring layer 223. Thus, a light condensed by the on-chip lens 228 is made incident from the wiring layer 223 side to the photoelectric conversion portion 222. The surface radiation type solid-state image pickup element 201 has the structure as described above.
However, an interval between adjacent two wirings 224 becomes narrow with the progress of miniaturization of the solid-state image pickup element. In addition, along with the progress of the multi-layer interconnection of the wiring layer 223, a distance between the on-chip lens 228 and the photoelectric conversion portion 222 becomes wider, so that a part Lx of a light L made obliquely incident hardly reaches the photoelectric conversion portion 222. For this reason, a phenomenon is generated in which light receiving characteristics such as shading are deteriorated.
A back surface radiation type solid-state image pickup element as shown in FIG. 8 is proposed as a structure useful in improving the deterioration of the light receiving characteristics. This back surface radiation type solid-state image pickup element, for example, is described in Japanese Patent Laid-Open No. Hei 6-283702. In the back surface radiation type solid-state image pickup element 101, signal processing portions 129, and a wiring layer 123 composed of wirings 124 and an insulating layer 125 are formed in a lower portion relative to a photoelectric conversion layer 122. In addition, a color filter 127 and an on-chip lens 128 are wired and disposed in this order on the photoelectric conversion portion 122. The back surface radiation type solid-state image pickup element 101 has a structure that the wiring layer 123 is not formed between the photoelectric conversion portion 122, and each of the color filter 127 and the on-chip lens 128 in such a manner. With this structure, an effective aperture ratio of 100% for an oblique light L can be attained. Thus, the sensitivity can be largely increased, and the generation of the shading can also be suppressed.
Then, a normal semiconductor substrate has a thickness which is as thick as several hundreds of micron meters, and thus may not transmit a light. For this reason, in the back surface radiation type CMOS solid-state image pickup element described above, a silicon substrate, for example, needs to be processed thinly to have a thickness of 10 μm or less because the light is radiated from the back surface of the silicon substrate. When the silicon substrate is processed thinly, if the thickness of the silicon layer disperses, the dispersion occurs in the incidence intensity of the light, and thus the nonconformity occurs in the form of the color shading.
On the other hand, for the purpose of preventing the thickness of the silicon layer from dispersing, a method using a Silicon On Insulator (SOI) substrate is devised. With this method, mechanical polishing having a high etching rate is carried out for the SOI substrate, Chemical Mechanical Polishing (CMP) processing is subsequently carried out, wet etching is then carried out, and the processing is stopped by an SiO2 layer, thereby preventing the thickness of the silicon layer from dispersing.
However, since the SOI substrate is more expensive than the normal semiconductor substrate, an increase in manufacture cost of the solid-state image pickup element due to use of the expensive SOI substrate becomes a problem.
Then, there is proposed a method of manufacturing a back surface radiation type solid-state image pickup element without using the SOI substrate for the purpose of reducing the substrate cost in the manufacture of the solid-state image pickup element. For example, there is proposed a method of providing a termination detecting portion having higher hardness than that of a substrate on a scribe line or in either a part of or the periphery of a pixel portion composed of a plurality of pixels, thereby manufacturing a back surface radiation type solid-state image pickup element. This method, for example, is described in Japanese Patent Laid-Open Nos. 2006-128392 and 2008-182142. With this method, when the semiconductor substrate is thinly processed from one surface side thereof by carrying out the CMP processing, the chemical mechanical polishing can be ended in the termination detecting portion in a self-aligned manner.